Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$101.59	5.275%	$106.9489	$106.95	$106.95	$106.90
Purchase #2	$95.60	7.763%	$103.0214	$103.02	$103.00	$103.00
Purchase #3	$40.79	12.590%	$45.9255	$45.93	$45.95	$45.90
Purchase #4	$76.30	5.581%	$80.5583	$80.56	$80.55	$80.60
Purchase #5	$53.91	3.418%	$55.7526	$55.75	$55.75	$55.80
Purchase #6	$240.77	5.631%	$254.3278	$254.33	$254.35	$254.30
Purchase #7	$186.29	3.395%	$192.6145	$192.61	$192.60	$192.60
7 purchase totals =	$795.25		$839.1490	$839.15	$839.15	$839.10